The European Union has said it is very close to signing a contract with drugs firms Pfizer and BioNTech for 300 million doses of a future new coronavirus vaccine.

"European science works," declared Ursula von der Leyen, the president of the European Commission, congratulating the US and German companies after they claimed a breakthrough.

The European Medicines Agency (EMA) has not yet received clinical trial data from Pfizer to approve the vaccine, which the manufacturer says has proved 90 per cent effective.

But Brussels has reserved hundreds of millions of doses of various potential vaccines from several companies and is close to turning its option with Pfizer and BioNTech into a contract.

Von der Leyen tweeted that the European Commission, the EU executive would "sign a contract with them soon for up to 300 million doses."

But, in a nod to the varying degrees of lockdown imposed in many EU member states to control the epidemic, she warned: "Let's keep protecting each other in the meantime."

EU health commissioner Stella Kyriakides described the companies' news as "encouraging", and said: "We are leaving no stone unturned to secure safe and efficient vaccines."

Earlier, officials had said that Brussels still expects to have to wait until early next year before it begins to roll out the vaccines, despite accelerating its approval procedure.

'Rolling reviews'

The EMA has begun an expedited procedure to examine potential vaccines and did nothing to pour cold water on the reports of a breakthrough.

But a spokeswoman for the Amsterdam-based agency said they had yet to receive the results of clinical trials. 

"Through rolling reviews, EMA can exceptionally evaluate data as it becomes available, ahead of a formal marketing-authorisation application," she said. 

"We evaluated the first batch of data on the vaccine, which came from laboratory studies (non-clinical data). 

"The agency is currently assessing a second batch of data which relate to the quality of the vaccine, including data related to its ingredients and the way it is produced. 

"Any new data available for this vaccine will be reviewed in the same way. We have not received nor assessed the emerging clinical data at this point and can therefore not comment further."

Separately, in Brussels, a European source confirmed this and added: "any prediction would be risky, but we have good indications that the first vaccine may be available early next year."

European officials, including von der Leyen have previously used this timeline when talking about a future vaccine.

And Brussels has put funding aside to reserve hundreds of millions of doses of future vaccines from several companies, including that from US giant Pfizer and its German partner BioNTech.